Intake manifold refill and holding control systems and methods

ABSTRACT

An engine control system for an auto-stop/start vehicle includes an auto-stop/start module and an actuator control module. The auto-stop/start module selectively generates an auto-stop command for shutting down an engine while an ignition is in an ON state. The actuator control module disables fuel to the engine when the auto-stop command is generated and closes a throttle valve to a predetermined throttle opening when the auto-stop command is generated.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.61/350,120, filed on Jun. 1, 2010. The disclosure of the aboveapplication is incorporated herein by reference in its entirety.

This application is related to U.S. patent application Ser. No.12/835,830 filed on Jul. 14, 2010, Ser. No. 12/835,835 filed on Jul. 14,2010, Ser. No. 12/835,842 filed on Jul. 14, 2010, Ser. No. 12/835,848filed on Jul. 14, 2010, Ser. No. 12/835,856 filed on Jul. 14, 2010, andSer. No. 12/835,951 filed on Jul. 14, 2010. The disclosures of the aboveapplications are incorporated herein by reference in their entirety.

FIELD

The present invention relates to internal combustion engines and moreparticularly to engine speed control systems and methods.

BACKGROUND

The background description provided herein is for the purpose ofgenerally presenting the context of the disclosure. Work of thepresently named inventors, to the extent it is described in thisbackground section, as well as aspects of the description that may nototherwise qualify as prior art at the time of filing, are neitherexpressly nor impliedly admitted as prior art against the presentdisclosure.

Air is drawn into an engine through an intake manifold. A throttle valvecontrols airflow into the engine. The air mixes with fuel from one ormore fuel injectors to form an air/fuel mixture. The air/fuel mixture iscombusted within one or more cylinders of the engine. Combustion of theair/fuel mixture may be initiated by, for example, injection of the fuelor spark provided by a spark plug.

An engine control module (ECM) controls the torque output of the engine.Under some circumstances, the ECM may shut down the engine betweenvehicle startup (e.g., key ON) and vehicle shutdown (e.g., key OFF). TheECM may selectively shut down the engine, for example, to increase fuelefficiency (i.e., reduce fuel consumption). The ECM may start the engineat a later time.

SUMMARY

An engine control system for an auto-stop/start vehicle includes anauto-stop/start module and an actuator control module. Theauto-stop/start module selectively generates an auto-stop command forshutting down an engine while an ignition is in an ON state. Theactuator control module disables fuel to the engine when the auto-stopcommand is generated and closes a throttle valve to a predeterminedthrottle opening when the auto-stop command is generated.

An engine control method for an auto-stop/start vehicle includes:selectively generating an auto-stop command for shutting down an enginewhile an ignition is in an ON state; disabling fuel to the engine whenthe auto-stop command is generated; and closing a throttle valve to apredetermined throttle opening when the auto-stop command is generated.

In still other features, the systems and methods described above areimplemented by a computer program executed by one or more processors.The computer program can reside on a tangible computer readable mediumsuch as but not limited to memory, nonvolatile data storage, and/orother suitable tangible storage mediums.

Further areas of applicability of the present disclosure will becomeapparent from the detailed description provided hereinafter. It shouldbe understood that the detailed description and specific examples areintended for purposes of illustration only and are not intended to limitthe scope of the disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure will become more fully understood from thedetailed description and the accompanying drawings, wherein:

FIG. 1 is a functional block diagram of an exemplary engine systemaccording to the principles of the present disclosure;

FIG. 2 includes exemplary graphs of engine speed and manifold absolutepressure (MAP) as functions of time according to the principles of thepresent disclosure;

FIG. 3 is a functional block diagram of an exemplary engine controlsystem according to the principles of the present disclosure;

FIG. 4 is an exemplary mode-flow diagram according to the principles ofthe present disclosure; and

FIG. 5 is a flowchart depicting an exemplary method of controlling theMAP according to the principles of the present disclosure.

DETAILED DESCRIPTION

The following description is merely exemplary in nature and is in no wayintended to limit the disclosure, its application, or uses. For purposesof clarity, the same reference numbers will be used in the drawings toidentify similar elements. As used herein, the phrase at least one of A,B, and C should be construed to mean a logical (A or B or C), using anon-exclusive logical or. It should be understood that steps within amethod may be executed in different order without altering theprinciples of the present disclosure.

As used herein, the term module refers to an Application SpecificIntegrated Circuit (ASIC), an electronic circuit, a processor (shared,dedicated, or group) and memory that execute one or more software orfirmware programs, a combinational logic circuit, and/or other suitablecomponents that provide the described functionality.

An engine control module (ECM) may selectively start and shut down anengine of a vehicle. For example only, the ECM may start and shut downthe engine when commanded to do so by a user, such as via a key or abutton. A key cycle may refer to a period between a first time when theuser commands vehicle startup and a second time when the user commandsvehicle shutdown.

The ECM may selectively shut down and start the engine during a keycycle under some circumstances. An auto-stop event refers to an engineshutdown performed during a key cycle. The ECM may selectively initiatean auto-stop event, for example, to decrease fuel consumption. Anauto-start event refers to an engine startup performed after anauto-stop event during a key cycle.

While the engine is shut down, pressure within an intake manifold of theengine approaches and may reach barometric pressure. With the pressureat or near barometric pressure when the engine is started, an air percylinder (APC) may be at or near an APC achieved when a throttle valveis in a wide open throttle (WOT) position.

During engine startup, the ECM may selectively set a spark timing to amaximum braking torque (MBT) spark timing. The combination of thepressure being at or near barometric pressure and the spark timing beingset to the MBT spark timing causes the engine speed to overshoot apredetermined engine speed. Overshooting the predetermined engine speedduring engine startup may be referred to as engine flare. A user mayexpect engine flare during engine startup. However, as torque may betransmitted between the engine and the transmission during auto-startevents, engine flare during an auto-start event may cause the vehicle toaccelerate or decelerate.

The ECM of the present disclosure disables fuel and spark to the enginewhen an auto-stop command is generated. The ECM selectively regulatesopening of the throttle valve to maintain the pressure within the intakemanifold below barometric pressure for as long as possible. Maintainingthe pressure below barometric pressure may provide more suitableconditions for engine startup when an auto-start command is generated.

Referring now to FIG. 1, a functional block diagram of an exemplaryengine system 100 is presented. An engine 102 generates drive torque fora vehicle. While the engine 102 is shown and will be discussed as aspark-combustion internal combustion engine (ICE), the engine 102 mayinclude another suitable type of engine, such as acompression-combustion ICE. One or more electric motors (ormotor-generators) may additionally generate drive torque.

Air is drawn into the engine 102 through an intake manifold 104. Airflowinto the engine 102 may be varied using a throttle valve 106. One ormore fuel injectors, such as fuel injector 108, mix fuel with the air toform an air/fuel mixture. The air/fuel mixture is combusted withincylinders of the engine 102, such as cylinder 110. Although the engine102 is depicted as including one cylinder, the engine 102 may includemore than one cylinder.

The cylinder 110 includes a piston (not shown) that is mechanicallylinked to a crankshaft 112. One combustion cycle within the cylinder 110may include four phases: an intake phase, a compression phase, acombustion (or expansion) phase, and an exhaust phase. During the intakephase, the piston moves toward a bottommost position and draws air intothe cylinder 110. During the compression phase, the piston moves towarda topmost position and compresses the air or air/fuel mixture within thecylinder 110.

During the combustion phase, spark from a spark plug 114 ignites theair/fuel mixture. The combustion of the air/fuel mixture drives thepiston back toward the bottommost position, and the piston drivesrotation of the crankshaft 112. Resulting exhaust gas is expelled fromthe cylinder 110 to complete the exhaust phase and the combustion event.A flywheel 116 is attached to and rotates with the crankshaft 112. Theengine 102 outputs torque to a transmission (not shown) via thecrankshaft 112.

An engine control module (ECM) 120 controls the torque output of theengine 102. The ECM 120 controls the throttle valve 106, the fuelinjector 108, and the spark plug 114 via a throttle actuator module 122,a fuel actuator module 124, and a spark actuator module 126,respectively. More specifically, the ECM 120 controls opening of thethrottle valve 106, fuel injection amount and timing, and spark timing.While not shown, the ECM 120 may also control other engine actuators,such as one or more camshaft phasers, an exhaust gas recirculation (EGR)valve, a boost device (e.g., a turbocharger or a supercharger), and/orother suitable engine actuators.

A crankshaft position sensor 130 monitors rotation of the crankshaft 112and outputs a crankshaft position signal based on rotation of thecrankshaft 112. The crankshaft position sensor 130 may also measuredirection of rotation of the crankshaft 112. The crankshaft positionsensor 130 may output a direction signal indicating the direction ofrotation, or the crankshaft position sensor 130 may indicate thedirection of rotation via the crankshaft position signal. The crankshaftposition may be used, for example, to determine rotational speed of thecrankshaft 112 (e.g., in revolutions per minute or RPM). The rotationalspeed of the crankshaft 112 may be referred to as engine speed. Amanifold absolute pressure (MAP) sensor 132 measures pressure within theintake manifold 104 and generates a MAP signal based on the pressure.

The ECM 120 may control the torque output of the engine 102 based on oneor more driver inputs, such as an accelerator pedal position (APP), abrake pedal position (BPP), and/or other suitable driver inputs. An APPsensor 134 measures position of an accelerator pedal (not shown) andgenerates an APP signal based on the position of the accelerator pedal.A BPP sensor 136 measures position of a brake pedal (not shown) andgenerates a BPP signal based on the position of the brake pedal.

The engine system 100 may include one or more other sensors 138, such asa mass air flowrate (MAF) sensor, an intake air temperature (IAT)sensor, an engine coolant temperature sensor, an engine oil temperaturesensor, and/or other suitable sensors. The ECM 120 may control thetorque output of the engine 102 based on one or more measuredparameters. The ECM 120 may communicate with one or more other modules,such as a transmission control module (TCM) 141.

A user may input vehicle startup and vehicle shutdown commands via anignition system 140 (collectively illustrated as ignition). For exampleonly, the user may input vehicle startup and vehicle shutdown commandsby turning a key, pressing a button, or in another suitable manner. Whenthe user has input a vehicle startup command and before a vehicleshutdown command has been received, the ignition system 140 may be in anON state. The ignition system 140 may be in an OFF state when a vehicleshutdown command is input. A period between a time when a vehiclestartup command is received and a later time when a vehicle shutdowncommand is received may be referred to as a key cycle.

When a vehicle startup command is received, the ECM 120 may start theengine 102. More specifically, the ECM 120 may activate and engage astarter 142 via a starter actuator module 144 when a vehicle startupcommand is received. The starter 142 drives rotation of the crankshaft112. The starter 142 may engage, for example, the flywheel 116. The ECM120 selectively begins supplying fuel to the engine 102 and initiatingcombustion as the starter 142 rotates the crankshaft 112. The ECM 120disables fuel and spark to the engine 102 when a vehicle shutdowncommand is received.

The ECM 120 may selectively shut down the engine 102 during a key cycle(i.e., before a vehicle shutdown command is received) under somecircumstances. An auto-stop event refers to shutting down the engine 102during a key cycle. For example only, the ECM 120 may selectivelyperform an auto-stop event during a key cycle when a user appliespressure to the brake pedal and/or when one or more other suitableconditions are satisfied. Shutting down the engine 102 under suchconditions may decrease fuel consumption.

The ECM 120 may later selectively terminate the auto-stop event andrestart the engine 102. An auto-start event refers to starting theengine 102 after an auto-stop event during a key cycle. For exampleonly, the ECM 120 may perform an auto-start event when the user releasesthe pressure from the brake pedal, when the user applies pressure to theaccelerator pedal, and/or when one or more other suitable conditions aresatisfied.

The MAP may approach barometric pressure when the engine 102 is shutdown. When engine startup is initiated (e.g., for an auto-start event orfor a vehicle startup command), the MAP may therefore be approximatelyequal to a MAP that may be present when the throttle valve 106 is in awide open throttle (WOT) position.

During engine startup, the ECM 120 may set the spark timing toapproximately a spark timing at which a maximum braking torque (MBT)will be produced under the operating conditions. This spark timing maybe referred to as an MBT spark timing. Setting the spark timing to theMBT spark timing during engine startup may ensure that a significantamount of torque is produced and that the engine 102 does not stall.

Referring now to FIG. 2, exemplary graphs of engine speed and MAP asfunctions of time are presented. Exemplary trace 202 tracks the enginespeed. Exemplary trace 206 tracks the MAP. An engine startup event isinitiated at approximately time T1. The starter 142 drives rotation ofthe crankshaft 112. A first combustion event within the engine 102occurs at approximately time T2, and the engine speed 202 increasestoward a predetermined speed as torque is produced.

Exemplary line 210 illustrates the predetermined engine speed. Forexample only, the predetermined engine speed 210 may be a predeterminedidle speed, such as approximately 700 RPM-900 RPM. The MAP being at ornear barometric pressure in combination with the spark timing atapproximately the MBT spark timing during engine startup may cause theengine speed 202 to overshoot the predetermined engine speed 210. Theengine speed 202 exceeds the predetermined engine speed 210 atapproximately time T3, and the engine speed 202 increases untilapproximately time T4.

The engine speed 202 begins decreasing at approximately time T4 and maydecrease to approximately the predetermined engine speed 210 under somecircumstances. The engine speed 202 may reach the predetermined enginespeed 210 at approximately time T5. Thus, the engine speed 202overshoots the predetermined engine speed 210 from approximately time T3to approximately time T5. Overshooting the predetermined engine speed210 during an engine startup may be referred to as engine flare.

In some vehicles, the transmission (and a torque transmission device,such as a torque converter) may be engaged to transmit torque betweenthe engine 102 and a driveline (not shown) when the engine 102 isstarted pursuant to an auto-start event. Engine flare under suchcircumstances may cause vehicle acceleration or deceleration, and theacceleration or deceleration may be experienced within a passenger cabinof the vehicle. Engine flare may also cause the MAP 206 to decrease asthe engine speed 202 overshoots the predetermined engine speed 210.

The ECM 120 of the present disclosure minimizes engine flare when theengine 102 is started. Exemplary trace 214 tracks engine speed ascontrolled by the ECM 120 to prevent engine flare and overshoot. The ECM120 of the present disclosure may smoothly increase the engine speed 214up to the predetermined engine speed 210 during engine startup tominimize engine flare and to minimize overshoot during engine startup.

Referring again to FIG. 1, the ECM 120 determines targets for opening ofthe throttle valve 106 (e.g., throttle position or throttle openingarea), air fuel ratio (AFR), and the spark timing during an enginestartup. The ECM 120 also determines a target engine speed based on apredetermined profile to be followed during the engine startup. Thepredetermined profile may be similar to the profile of the engine speed214 of FIG. 2 or another suitable profile that may smoothly transitionthe engine speed up to the predetermined engine speed during an enginestartup.

The ECM 120 determines a spark correction based on the target enginespeed. More specifically, the ECM 120 determines the spark correctionbased on a difference between the target engine speed and the measuredengine speed. The ECM 120 adjusts the target spark timing based on thespark correction and sets the spark timing to the adjusted spark timing.In this manner, the ECM 120 controls the engine speed to track thepredetermined profile and to minimize overshoot engine startup.

Referring now to FIG. 3, a functional block diagram of an exemplaryengine control system 300 is presented. The ECM 120 may include anengine speed determination module 302, a target engine speed module 306,an actuator control module 310, an engine load estimation module 314, amode control module 318, and an auto-stop/start module 320. The ECM 120may also include a correction disabling module 322, a correctiondetermination module 326, and a spark timing adjustment module 330.

The engine speed determination module 302 determines the engine speed.The engine speed determination module 302 may determine the engine speedbased on the crankshaft position signal. For example only, thecrankshaft position sensor 130 may generate a pulse in the crankshaftposition signal when a tooth of an N-toothed wheel (e.g., the flywheel116) passes the crankshaft position sensor 130. The engine speeddetermination module 302 may determine the engine speed based on aperiod between two or more of the pulses.

The target engine speed module 306 determines the target engine speedbased on a control mode. The target engine speed module 306 maydetermine the target engine speed further based on a driver torquerequest, the engine coolant temperature, the oil temperature, and/or oneor more other suitable parameters. The driver torque request may bedetermined based on the APP, the BPP, cruise control inputs, and/or oneor more other driver inputs.

The actuator control module 310 determines a target spark timing, atarget throttle opening, and a target fueling. The actuator controlmodule 310 may determine the target spark timing, the target throttleopening, and/or the target fueling based on the target engine speed, theengine speed, and the control mode. The actuator control module 310 maydetermine the target spark timing, the target throttle opening, and/orthe target fueling further based on an engine load, the MAP, and/or oneor more other parameters. For example only, a mass of air per cylinder(APC) for a given combustion event may be determined based on the MAP.The actuator control module 310 may set the target fueling for thecombustion event based on the APC to achieve a stoichiometric air/fuelmixture. The engine load estimation module 314 may estimate the engineload based on the engine speed and/or one or more suitable parameters,such as transmission load. Transmission load may refer to the load(e.g., torque) imposed on the engine 102 via the transmission.

The mode control module 318 may provide the control mode to the actuatorcontrol module 310. FIG. 4 includes an exemplary mode-flow diagram. Forexample only, as shown in the example of FIG. 4, the control modes mayinclude a throttle holding mode 402, a manifold refill mode 406, a MAPholding mode 410, a choking mode 414, a cranking airflow mode 418, and aspeed control mode 422. The mode control module 318 may set the controlmode based on the engine speed, the MAP, auto-stop/start commands, andone or more other suitable parameters.

The auto-stop/start module 320 may selectively generate an auto-stopcommand during a key cycle. For example only, the auto-stop/start module320 may generate an auto-stop command when the APP is approximatelyequal to a predetermined zero APP and the BPP is greater than apredetermined zero BPP while the vehicle speed is less than apredetermined speed. The predetermined zero APP may correspond to theAPP when no pressure is being applied to the accelerator pedal. Thepredetermined zero BPP may correspond to the BPP when no pressure isbeing applied to the brake pedal.

The mode control module 318 initiates an auto-stop event when anauto-stop command is generated. The mode control module 318 may initiatethe auto-stop event by setting the control mode to the throttle holdingmode 402. The actuator control module 310 disables the provision of fueland spark to the engine 102 when the control mode is set to the throttleholding mode 402. The actuator control module 310 may set the targetthrottle opening to a first predetermined throttle opening when thecontrol mode is set to the throttle holding mode 402. For example only,the first predetermined throttle opening may include a predeterminedidle throttle opening or another suitable throttle opening. Disablingthe provision of fuel and spark to the engine 102 allows the enginespeed to decrease toward zero as no torque is being produced by theengine 102. Setting the target throttle opening to the firstpredetermined throttle opening chokes the engine 102 and minimizesshudder. Shudder may refer to vibration experienced within the passengercabin as the engine speed approaches zero.

The mode control module 318 may maintain the control mode in thethrottle holding mode 402 until the engine speed reaches zero. Theengine 102 may be deemed shut down when the engine speed is equal tozero. During the throttle holding mode 402 (i.e., before the enginespeed reaches zero), the mode control module 318 may selectivelytransition the control mode to the speed control mode 422. Such atransition from the throttle holding mode 402 to the speed control mode422 is illustrated in the example of FIG. 4 by line 430. For exampleonly, the mode control module 318 may transition the control mode to thespeed control mode 422 when the auto-stop/start module 320 generates anauto-start command.

The auto-stop/start module 320 may generate an auto-start command, forexample, when the BPP approaches or reaches the predetermined zero BPPand/or when the APP is greater than the predetermined zero APP duringthe throttle holding mode 402. The target engine speed module 306 mayset the target engine speed to the predetermined engine speed or toanother speed when the control mode is set to the speed control mode422.

The mode control module 318 may selectively transition the control modeto the manifold refill mode 406 when the engine speed reaches zeroduring the throttle holding mode 402. When the control mode is set tothe manifold refill mode 406, the actuator control module 310 may setthe target throttle opening to a second predetermined throttle opening.For example only, the second predetermined throttle opening may includethe WOT opening or another suitable throttle opening that allows the MAPto increase toward barometric pressure. The second predeterminedthrottle opening is greater than the first predetermined throttleopening.

The mode control module 318 starts a timer in a timer module 334 whenthe mode control module 318 transitions the control mode from thethrottle holding mode 402 to the manifold refill mode 406. The timertracks the period elapsed since the control mode was set to the manifoldrefill mode 406. During the manifold refill mode 406, the mode controlmodule 318 may selectively transition the control mode to the chokingmode 414 when the timer is less than a predetermined period. For exampleonly, the mode control module 318 may transition the control mode to thechoking mode 414 when the auto-stop/start module 320 generates anauto-start command. In this manner, if the engine 102 should beauto-started when the control mode has been set to the manifold refillmode 406 for less than the predetermined period, the MAP holding mode410 may be skipped in favor of the choking mode 414. Such a transitionfrom the manifold refill mode 406 to the choking mode 414 is illustratedin the example of FIG. 4 by line 434. The choking mode 414 is discussedfurther below. For example only, the period may be approximately 6seconds.

If the MAP exceeds a first predetermined pressure during the manifoldrefill mode 406, the mode control module 318 may transition the controlmode to the MAP holding mode 410. For example only, the firstpredetermined pressure may be a predetermined amount or percentage lessthan barometric pressure.

When the control mode is set to the MAP holding mode 410, the actuatorcontrol module 310 may set the target throttle opening to a fully closedthrottle opening. Setting the target throttle opening to the fullyclosed throttle opening may be performed to maintain the MAP atapproximately the first predetermined pressure and below barometricpressure in anticipation of auto-starting the engine 102.

Despite the throttle valve 106 being fully closed, however, the MAP mayincrease toward barometric pressure. For example only, a MAP increasemay be attributable to inflow through open intake and exhaust valvesand/or through the throttle valve 106. Accordingly, the MAP may increasetoward barometric pressure during the MAP holding mode 410.

When an auto-start command is generated by the auto-stop/start module320, the mode control module 318 initiates an auto-start event. The modecontrol module 318 may start the engine (e.g., for an auto-start eventor a vehicle startup command) by setting the control mode to the chokingmode 414. The actuator control module 310 may set the target throttleopening to the fully closed throttle opening when the control mode isset to the choking mode 414. The actuator control module 310 may alsocrank the engine 102 via the starter 142 when the control mode is set tothe choking mode.

Cranking the engine 102 while the throttle valve 106 is fully closedcauses the MAP to decrease. The actuator control module 310 beginssupplying fuel to the engine 102 during the choking mode 414. Theactuator control module 310 sets the target spark timing for eachcombustion event that occurs after the control mode is transitioned tothe choking mode 414.

The mode control module 318 may transition the control mode to thecranking airflow mode 418 when the MAP falls below a secondpredetermined pressure during the choking mode 414. The secondpredetermined pressure may be less than the first predeterminedpressure. The actuator control module 310 may continue cranking theengine 102 during the cranking airflow mode 418.

The actuator control module 310 may set the target throttle openingbased on the target engine speed during the cranking airflow mode 418.In other words, the actuator control module 310 selectively opens thethrottle valve 106 during the cranking airflow mode 418 and allowsairflow into the intake manifold 104 during the cranking airflow mode418. The mode control module 318 may set the control mode to the speedcontrol mode 422 after the cranking airflow mode 418.

The correction disabling module 322 selectively enables and disables thecorrection determination module 326 based on the control mode. Morespecifically, the correction disabling module 322 enables the correctiondetermination module 326 when the control mode is set to the chokingmode 414 or to the cranking airflow mode 418. Written conversely, thecorrection disabling module 322 may disable the correction determinationmodule 326 when the control mode is set to the throttle holding mode402, the manifold refill mode 406, or the MAP holding mode 410. In thismanner, the correction disabling module 322 enables the correctiondetermination module 326 when the engine 102 is started pursuant to avehicle startup command or to an auto-start event.

The actuator control module 310 may determine the target spark timingbased upon an inverse of a relationship between torque and the targetspark timing. For example only, the actuator control module 310 maydetermine a target amount of torque and determine the target sparktiming based on the relationship:S _(T) =T ⁻¹(T _(T) ,APC,I,E,AF,OT,#),where S_(T) is the target spark timing, T⁻¹ is an inverse torque model,T_(T) is the target torque, APC is the air per cylinder (APC), I and Eare intake and exhaust phaser positions, respectively, AF corresponds tothe air/fuel mixture, OT is the oil temperature, and # is the number ofcylinders that will be capable of producing torque (i.e., supplied fuel)when the target spark timing is executed for the one of the cylinders.This relationship may be embodied as an equation and/or as a lookuptable. The actuator control module 310 may determine the target torquebased on, for example, the engine speed, the target engine speed, thedriver torque request, one or more engine operating parameters, and/orother suitable parameters.

When enabled, the correction determination module 326 determines a sparktiming correction based on the engine speed and the target engine speed.More specifically, the correction determination module 326 determinesthe spark timing correction based on a difference between the targetengine speed and the engine speed.

The correction determination module 326 may determine the spark timingcorrection using a proportional control scheme based on the differencebetween the target engine speed and the engine speed. For example only,the correction determination module 326 may determine the spark timingcorrection using the equation:Correction=k*(Target−Actual),where Correction is the spark timing correction, k is a proportionalgain, Target is the target engine speed, and Actual is the engine speed.

The spark timing adjustment module 330 receives the target spark timingand the spark timing correction. The spark timing adjustment module 330adjusts the target spark timing based on the spark timing correction andoutputs an adjusted spark timing. For example only, the spark timingadjustment module 330 may determine the adjusted spark timing based on asum of the spark timing correction and the target spark timing.

The spark timing adjustment module 330 may provide the adjusted sparktiming to the spark actuator module 126. The spark actuator module 126provides spark at the adjusted spark timing. In this manner, the sparktiming is adjusted to shape the engine speed toward the target enginespeed and to minimize overshoot and engine flare during engine startup.

While the principles of the present disclosure are discussed as relatingto adjusting spark timing, the principles of the present disclosure arealso applicable to adjusting fuel injection timing incompression-combustion engines. For example only, the fuel injectiontiming may be adjusted based on an injection timing correction that isdetermined based on the difference between the target engine speed andthe engine speed in compression-combustion engine systems.

Referring now to FIG. 5, a flowchart depicting an exemplary method 500of controlling the MAP is presented. Control may begin with 502 wherecontrol determines whether an auto-stop event has been commanded duringa key cycle. If true, control may continue with 506; if false, controlmay end. Control may set the control mode to the throttle holding modewhen 502 is true.

Control disables the provision of fuel and spark to the engine 102 at506 to shut down the engine 102 and to perform the commanded auto-stopevent. Control may set the target throttle opening equal to the firstpredetermined throttle opening at 510. The first predetermined throttleopening may include, for example, a predetermined idle throttle openingor another suitable throttle opening.

Control may determine whether an auto-start event has been commanded at514. If true, control may end; if false, control may continue with 518.While control is shown and described as ending when 514 is true, controlmay transition the control mode to the speed control mode when 514 istrue. Control may determine whether the engine speed is approximatelyequal to zero (i.e., less than a predetermined speed) at 518. If true,control may continue with 522; if false, control may return to 514.Control may set the control mode to the manifold refill mode when 518 istrue. For example only, the predetermined speed may be approximately30-50 RPM. Below the predetermined speed, the engine speed may be deemedapproximately equal to zero, for example, because the determined enginespeed may be imprecise under the predetermined speed.

Control increases the target throttle opening at 522. Increasing thethrottle opening allows the MAP to increase toward barometric pressure.Control may start a timer at 526. The timer tracks the period of timeelapsed since the control mode was set to the manifold refill mode(i.e., the period that the MAP has been allowed to increase towardbarometric pressure). Control may determine whether an auto-start hasbeen commanded at 530. If true, control may end; if false, control maycontinue with 534. While control is shown and described as ending when530 is true, control may set the control mode to the choking mode when530 is true.

Control may determine whether the MAP is greater than a predeterminedpressure at 534. If true, control may continue with 538; if false,control may return to 530. The predetermined pressure may be, forexample, a predetermined amount or percentage less than barometricpressure or a predetermined idle MAP. Control may alternativelydetermine whether the timer is greater than a predetermined period at534. If true, control may continue with 538; if false, control mayreturn to 530. Control may set the predetermined period based on the MAPbefore the target throttle opening was increased. Control may transitionthe control mode to the MAP holding mode when 534 true. Control sets thetarget throttle opening to the fully closed throttle opening at 538, andcontrol may end. In the above manner, control attempts to maintain theMAP below barometric pressure in anticipation of starting the enginepursuant to an auto-start command.

The broad teachings of the disclosure can be implemented in a variety offorms. Therefore, while this disclosure includes particular examples,the true scope of the disclosure should not be so limited since othermodifications will become apparent to the skilled practitioner upon astudy of the drawings, the specification, and the following claims.

What is claimed is:
 1. An engine control system for an auto-stop/startvehicle, comprising: an auto-stop/start module that selectivelygenerates an auto-stop command for shutting down an engine while anignition is in an ON state and that selectively generates an auto-startcommand for re-starting the engine after the generation of the auto-stopcommand; and an actuator control module that, in response to thegeneration of the auto-stop command and before the generation of theauto-start command: disables fuel to the engine; closes a throttle valveto a predetermined idle throttle opening; maintains the throttle valveat the predetermined idle throttle opening until an engine speed is lessthan a predetermined speed; selectively opens the throttle valve withrespect to the predetermined idle throttle opening when the engine speedis less than the predetermined speed; and closes the throttle valve to afully closed position when a manifold absolute pressure (MAP) exceeds apredetermined pressure while the throttle valve is open with respect tothe predetermined idle throttle opening.
 2. The engine control system ofclaim 1 wherein the actuator control module maintains the throttle valveat the fully closed position after the MAP exceeds the predeterminedpressure.
 3. The engine control system of claim 2 wherein, when theauto-stop/start module selectively generates the auto-start commandafter the MAP exceeds the predetermined pressure, the actuator controlmodule activates a starter when the auto-start command is generated andmaintains the throttle valve at the fully closed position after theauto-start command is generated.
 4. The engine control system of claim 1wherein, when the auto-stop/start module selectively generates theauto-start command after the engine speed is less than the predeterminedspeed, the actuator control module activates a starter when theauto-start command is generated and closes the throttle valve to thefully closed position when the auto-start command is generated.
 5. Theengine control system of claim 1 wherein, when the auto-stop/startmodule selectively generates the auto-start command before the enginespeed is less than the predetermined speed, the actuator control moduleselectively provides fuel and spark to the engine when the auto-startcommand is generated and selectively opens the throttle valve withrespect to the predetermined idle throttle opening when the auto-startcommand is generated.
 6. The engine control system of claim 1 wherein,when the auto-stop/start module selectively generates the auto-startcommand before the engine speed is less than the predetermined speed,the actuator control module selectively provides fuel and spark to theengine when the auto-start command is generated and selectively opensthe throttle valve with respect to the predetermined idle throttleopening when the auto-start command is generated.
 7. An engine controlmethod for an auto-stop/start vehicle, comprising: selectivelygenerating an auto-stop command for shutting down an engine while anignition is in an ON state; selectively generating an auto-start commandfor re-starting the engine after the generation of the auto-stopcommand; and in response to the generation of the auto-stop command andbefore the generation of the auto-start command: disabling fuel to theengine; closing a throttle valve to a predetermined idle throttleopening; maintaining the throttle valve at the predetermined idlethrottle opening until an engine speed is less than a predeterminedspeed; selectively opening the throttle valve with respect to thepredetermined idle throttle opening when the engine speed is less thanthe predetermined speed; and closing the throttle valve to a fullyclosed position when a manifold absolute pressure (MAP) exceeds apredetermined pressure while the throttle valve is open with respect tothe predetermined idle throttle opening.
 8. The engine control method ofclaim 7 further comprising maintaining the throttle valve at the fullyclosed position after the MAP exceeds the predetermined pressure.
 9. Theengine control method of claim 8 further comprising: selectivelygenerating the auto-start command after the MAP exceeds thepredetermined pressure; activating a starter when the auto-start commandis generated; and maintaining the throttle valve at the fully closedposition after the auto-start command is generated.
 10. The enginecontrol method of claim 7 further comprising, when the auto-startcommand is generated after the engine speed is less than thepredetermined speed: activating a starter when the auto-start command isgenerated; and closing the throttle valve to the fully closed positionwhen the auto-start command is generated.
 11. The engine control methodof claim 7 further comprising, when the auto-start command is generatedbefore the engine speed is less than the predetermined speed:selectively providing fuel and spark to the engine when the auto-startcommand is generated; and selectively opening the throttle valve withrespect to the predetermined idle throttle opening when the auto-startcommand is generated.
 12. The engine control method of claim 7 furthercomprising, when the auto-start command is generated before the enginespeed is less than the predetermined speed: selectively providing fueland spark to the engine when the auto-start command is generated; andselectively opening the throttle valve with respect to the predeterminedidle throttle opening when the auto-start command is generated.